1. Field of the Invention
The present invention relates to a laminate type varistor adapted for being incorporated into a small-capacitance high-frequency circuit, or the like.
2. Description of the Related Art
Conventionally, as shown in FIG. 5, a laminate type varistor is configured in the following manner. That is, at least two inner electrodes 20a and 20b making a pair to each other and a varistor layer 21 are laminated. Ceramic layers 22 and 23 are provided as outermost layers for protecting the laminate. The inner electrodes 20a and 20b are electrically connected to outer electrodes 24 and 25 respectively. The varistor layer 21 has a dielectric constant. The inner electrodes 20a and 20b are formed to have surfaces W facing each other through the varistor layer 22 (Unexamined Japanese Patent Publication (kokai) Nos. Hei. 5-6806 and Hei. 5-6807).
Similarly, conventionally, also in the case where pairs of inner electrodes 30a, 30b; 31a, 31b; . . . are provided in a laminate type varistor as shown in FIG. 6. The laminate type varistor is configured in the following manner. That is, the inner electrodes 30a, 30b; 31a, 31b; . . . are formed so that the inner electrodes have surfaces W facing each other through varistor layers 32a, 32b . . . respectively. Protection ceramic layers 33 and 34 are provided as outermost layers. The inner electrodes 30a, 30b; 31a, 31b; . . . are electrically connected to outer electrodes 35 and 36 respectively (Unexamined Japanese Patent Publication (kokai) Nos. Hei. 5-283208 and Hei. 8-55710).
In the laminate type varistor configured as described above, the capacitance increases as the facing surfaces W of the inner electrodes 20a, 20b, 30a, 30b, 31a, 31b . . . increase in terms of areas. However, if the capacitance is large, a high-frequency signal may be passed through the varistor or the waveform of the signal may be distorted in the case where the varistor is used in a high-frequency circuit. To prevent this problem, it is necessary to set the capacitance to a value of about several tens of pF. In the aforementioned configuration, however, it is difficult to set the capacitance to a value of about several tens of Pf.
It is an object of the present invention to provide a laminate type varistor in which capacitance can be set to a small value while a varistor voltage is kept in a value equivalent to that of a conventional varistor.
A laminate type varistor according to the present invention comprises at least one pair of first and second inner electrodes; a varistor layer, the at least one pair of first and second electrodes and the varistor layer being laminated; and a first outer electrode and a second outer electrode electrically connected to the first inner electrode and a second inner electrode, respectively, wherein the first inner electrode and the first inner electrode are separated by a predetermined distance from the outer electrode so that the first inner electrode has no electrode surface facing to an electrode surface of the second inner electrode.
A laminate type varistor according to the present invention comprises: a ceramic sintered body comprising at least one pair of first and second inner electrodes; a varistor layer, the at least one pair of first and second electrodes and the varistor layer being laminated; and protection ceramic layers as outermost layers of the ceramic sintered body; and a first outer electrode and a second outer electrode electrically connected to the first inner electrode and a second inner electrode, respectively; wherein a width of the ceramic sintered body is equal to or longer than the sum of the lengths of the first and second inner electrodes.